1. Field of the Invention
The present invention is directed to on-site treatment of drilling fluids, mobile systems for treating drilling fluids, methods of their use, and, in certain particular aspects, to such systems and methods that have erectable parts to facilitate fluid processing.
2. Description of Related Art
The prior art discloses a wide variety of systems for treating drilling fluids and methods of their use; for example, and not by way of limitation, see the systems and methods in U.S. Pat. Nos. 7,296,640; 7,022,240; 6,881,349; 6,863,809; 6,808,626; 6,855,261; 6,391,195; 6,193,070; 6,059,977; 5,093,008; 4,595,422; 4,536,286; and 4,474,254—all of said patents incorporated fully herein for all purposes.
Oil and gas well exploration involves the generation of various fluids and of waste products, including, e.g., fluid wastes, spent drilling fluids, and fracture or return fluids from various operations. Fluids, etc. have been treated and processed both on-site and off-site. U.S. Pat. No. 4,465,598 discloses an off-site method for the precipitation of metals including iron, nickel, chromium, cobalt, and manganese in oil and gas well heavy brines which have been filtered initially to remove solids. U.S. Pat. No. 4,634,533 discloses an oil and gas well brine treatment including an initial oxidizing treatment to convert iron to the ferric state. U.S. Pat. No. 5,814,230 describes an apparatus and method for separation of solids from liquid for use with different processes and describes the separation of solids from a liquid flow using an endless conveyor carrying screen filters which dredge gravity-settled solids from the bottom of a settling tank and filter solids suspended in the flowing liquid. The solids are further dewatered while on the filters using a combination of vibration and air streams. U.S. Pat. No. 4,436,635 describes a filtering process for filtration of oil and gas well treatment fluids.
Treating fluids, etc., off-site can be uneconomical due to transportation costs. Consequently mobile systems for on-site treatment have been developed, some of which attempt to produce fluid re-usable on-site. U.S. Pat. No. 4,895,665 discloses on-site methods for treating and reclaiming oil and gas well working fluids and the related drilling pits and methods of chemical treatment and filtration of oil and gas well working fluids within associated drilling pits. These methods include preparing a drilling pit for closure through reduction of the fluid content in sludge which is formed in the drilling pit. Treated water can be reused.
U.S. Pat. No. 5,093,008 describes on-site processes and apparatus for recovering reusable water from waste drilling fluid. The processes involve a dewatering process and apparatus for concurrent reutilization of water in waste drilling fluids from an active drilling operation that includes a storage area, an intermixer for introducing treatment chemicals into the waste drilling fluids, and a centrifuge. Flocculation is chemically induced in the waste drilling fluids as they pass through the intermixing needs for introducing treatment chemicals into the waste drilling fluids. The waste drilling fluids are then transferred to a centrifuge where solid waste is separated from clear, reusable water. The water is returned to the storage area and may be chemically adjusted prior to being returned to the drilling rig.
U.S. Pat. No. 4,536,286 describes a self-contained, portable waste treatment system for hazardous and non-hazardous waste with a pair of mixing tanks. Solids are removed from fluid waste streams by flocculation and related solids deposition.
U.S. Pat. No. 7,022,240 discloses an apparatus and method for on-site treatment and reclamation of oil and gas well waste water or fracturing fluids. The mobile treatment process and apparatus provide both chemical precipitation and filtration to treat the drilling fluid waste to a technically and environmentally acceptable level allowing for reuse. Alkaline treating agents are applied to the drilling waste fluids, as they are pumped through the treatment apparatus, to increase the pH of the fluid waste to a preferred pH range and to also cause selective soluble contaminants in the fluids to form a precipitate. The waste fluid is allowed to clarify as the precipitate of insoluble contaminants, through flocculation, settle and form a sludge at the bottom of the drilling pit. The clarified fluids are then filtered to satisfy applicable industry and environmental requirements.
Single skid mounted apparatus for providing all the components necessary to treat used drilling mud and return a clarified liquid for reuse in an active mud system are disclosed in prior references; e.g., see U.S. Pat. Nos. 4,536,286; 4,474,254; 5,582,727; 6,391,195; and 6,863,809. For example, U.S. Pat. No. 4,536,286 discloses a transportable waste treatment which is completely mobile and capable of treating high mud volumes. This system is self-contained having chemical storage, chemical pumps, sludge pumps, water pumps, laboratory, centrifuge, conveyors etc. and has weight, height and width suitable for highway travel. A skid incorporates three settling tanks and two chemical tanks for flocculation. Waste liquids containing solids enter a first settling tank and are mixed with flocculation chemicals. Solids settle to the tapered bottom of the tank for collection by a suction located at the apex of the tank bottom. Partially clarified liquid from the first settling tank overflows a weir to the next adjacent settling tank and similarly for the second to the third settling tank.
U.S. Pat. No. 5,582,727 discloses a single structural skid with four settling tanks, each equipped with a shaker and a de-silter. Used drilling mud is routed sequentially from tank to tank. Partially clarified liquid is decanted over weirs to each tank in succession. Fixed suction pumps extract settled solids from the bottom of each tank and route them to the de-silter of each additional and successive tank. Foster does not practice flocculation.
U.S. Pat. No. 6,391,195 discloses an apparatus for cleaning clearwater drilling muds and a process for treating used drilling mud, particularly that produced during clearwater drilling. A structural and highway transportable skid has two or more settling tanks connected in succession. Flocculation aids settling of solids to the bottom and clarified liquid forms at the surface. Clarified liquid flows from one tank to the next successive tank. Clarified liquid is produced from the last of the successive settling tanks. The tanks have flat bottoms. Passageways extend between each successive tank for gravity-flowing liquid from one tank to successive settling tank. A solids tank or centrifuge is also mounted within the skid. The solids and settling tanks are located for weight-balancing. A rotational suction is positioned in the bottom of each settling tank and having one or more radially extending conduits which rotate about an axis and have inlets at their distal ends which traverse an inscribed circular path about the periphery of the tank's bottom. Collected solids are directed to the solids tank and a drag conveyor transporting solids product outside the skid.
There has long been a need, recognized by the present inventors, for effective and efficient systems for on-site treatment and processing of well fluids. There has long been a need, recognized by the present inventors, for effective and efficient unitized skid-mounted systems for processing well fluids with centrifuge apparatus.
U.S. Pat. No. 6,863,809 discloses transportable drilling fluid cleaning systems for removing solids from drilling fluid at a drill site comprises a platform for transporting the system. A bin region on the platform retains solids from the drilling fluid. A settling tank on the platform separates the drilling fluid into an upper fluid fraction having a reduced concentration of solids and a lower solids fraction having a higher concentration of solids as the drilling fluid flows from an inlet chamber for receiving drilling fluid to at least one other chamber. A stand on the platform supports at least one centrifuge for separating the solids from the drilling fluid, the stand being movable between stored and operating positions. The system provides a self-contained unit that is easily transportable on a flat bed truck to provide all the ancillary equipment necessary for solids control at the drill site. In certain aspects such systems include: a platform for transporting the cleaning system to a drill site; a bin region on the platform to retain solids from the drilling fluid; a settling tank on the platform having an inlet chamber to receive drilling fluid and at least one other chamber, the settling tank acting to separate the drilling fluids into an upper fluid fraction having a reduced concentration of solids and a lower solids fraction having a higher concentration of solids as the drilling fluid flows from the inlet chamber to at least one other chamber; and a stand on the platform to support at least one centrifuge for separating the solids from the drilling fluid, the stand being movable between a stored position during transport of the platform and an operating position. In certain of these systems, the platform is skid loadable onto a trailer towable by a vehicle to move the system as a unit.